Method of making flat loop bipolar electrode tips for electrosurgical instrument

ABSTRACT

A method is provided for making an electrode tip for use in a bipolar electrosurgical instrument from a single flat blank of metal. The method uses a photo chemical machining process. The resultant electrode tip has a generally loop shaped working portion. Use of the flat blank of metal results in electrodes having working portions with sharp edges in cross-section. The working portions emit concentrated energy in the radial direction.

This is a division of application Ser. No. 08/658,429, filed Jun. 5,1996 now U.S. Pat. No. 5,733,283.

FIELD OF THE INVENTION

The present invention relates generally to electrosurgical instruments,and, in particular to an electrode tip for a bipolar electrosurgicalcutting/coagulating instrument particularly adaptable for use inconstricted areas and a method of making an electrode tip by a photochemical machining process.

BACKGROUND OF THE INVENTION

Electrosurgery is one form of a surgical cutting and coagulatingprocedure. Electrosurgery has two primary modes--monopolar and bipolar.Monopolar surgery uses an instrument, with a single electrode such as asingle loop instrument, and a grounding pad as the means to administerthe output of a surgical generator to the patient. In contrast, bipolarinstruments include two electrodes in close proximity to each other.Typically, one electrode is a supply electrode and the other electrodeis a return electrode. Bipolar instruments operate at much lower powerlevels than monopolar instruments and thus do not disturb nearby tissue.Examples of bipolar instruments are shown in U.S. Pat. Nos. 5,290,286(Parins); 5,192,280 (Parins); 5,013,312 (Parins et al.); 5,282,799(Rydell); 5,071,419 (Rydell) and WO 93/13719 (Fleenor et al.).

Wire electrodes, which are used in some such instruments, are generallyrounded in cross-section and thus do not concentrate energy in anyparticular radial direction. Rounded electrodes also present arelatively large contact area to the surgical site. This may beundesirable if the area of interest is very small. Furthermore, it isdifficult to make a wire electrode which has a very small diameter(i.e., width). The smaller the diameter, the smaller the cross-sectionalarea and the finer the electrode. Finer electrodes make finer cuts. Aninstrument with very fine electrodes can be used in tight crevices andin small areas, such as certain predefined regions of the brain. It isalso a desirable goal for electrodes to have low resistance so that onlya small amount of power need be applied to the electrodes to effectivelycut and coagulate the desired tissue. By using less power at thesurgical site, the device can be used in delicate surgical procedures,such as neurosurgery, with less risk of damaging neighboring areas.

Despite the variety of electrodes known in the prior art, there is stilla need for a finer electrode which can also concentrate energy in theradial direction, is easy and inexpensive to fabricate, and hasrelatively low resistance. The present invention fills this need byproviding an electrode tip with very fine electrodes that have sharpedges in cross-section and are preferably fabricated by photo chemicalmachining.

SUMMARY OF THE INVENTION

The present invention in one embodiment provides an electrode for amicrosurgical instrument. The electrode has a working portion that isgenerally loop shaped and has sharp edges in cross-section.

Another embodiment of the invention provides an electrode tip comprisinga first and a second electrode. The first electrode has a workingportion that is generally loop shaped and has sharp edges incross-section. The second electrode generally surrounds at least a partof the working portion of the first electrode and is generally spacedfrom and coplanar with the first electrode.

Yet another embodiment of the invention comprises an electrosurgicalinstrument having a handle and an electrode tip. The handle has aproximal end and a distal end. The electrode tip includes a firstelectrode and a second electrode. The first and second electrodes eachextend from the distal end and have a working portion that is generallyloop shaped and generally rectangular in cross-section. The first andsecond electrodes are adapted to be connected to opposite poles of abipolar generator. The second electrode generally surrounds at least apart of the working portion of the first electrode and is generallyspaced from and coplanar with the first electrode.

Yet another embodiment of the invention comprises a handle and anelectrode tip. The handle has a proximal end and a distal end. Theelectrode tip includes a first and a second electrode, each extendingfrom the distal end, having a working portion that is generally loopshaped and being rectangular in cross-section. The first and secondelectrodes are adapted to be connected to opposite poles of a bipolargenerator. The second electrode is generally hook shaped, generallyhooks around the first electrode, and is generally spaced from andcoplanar with the first electrode.

Yet other embodiments of the invention provide methods of fabricatingelectrodes from a metal blank. In one exemplary fabrication method, anelectrode tip is fabricated from a metal blank. The method comprises thesteps of defining a pattern, the pattern including an electrode tip, andmachining the metal blank as defined by the pattern to form at least theelectrode tip. The resultant electrode tip has sharp edges incross-section.

In another exemplary fabrication method, an electrode is fabricated froma metal blank. The method comprises the steps of creating at least onepattern, the pattern including at least an electrode pattern, placing anegative of the pattern against opposite facing surfaces of a metalblank coated with a photoresist material, the negative of the pattern onthe opposite facing surfaces being in registration with each other,exposing and developing the metal blank, and removing photoresist fromunexposed, undeveloped areas of the metal blank. Next, the metal blankis exposed to a metal dissolving chemical that etches away theunexposed, undeveloped areas of the metal blank. The resultant piece ofmetal is suitable for use as at least one electrode and has a shape ofthe at least one created electrode pattern, and has sharp edges incross-section.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the invention, will be better understood whenread in conjunction with the appended drawings. For the purpose ofillustrating the invention, there are shown in the drawings embodimentswhich are presently preferred. It should be understood, however, thatthe invention is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1 is a perspective view of an electrosurgical instrument inaccordance with a preferred embodiment of the present invention, shownattached to a bipolar generator and ready for use;

FIG. 2 is a transverse sectional view of an electrosurgical instrumentin accordance with another preferred embodiment of the presentinvention, prior to removal of its protective electrode tip guard;

FIG. 3 is an exploded perspective view of the instrument of FIG. 2;

FIG. 4 is an enlarged perspective view of electrodes used in anelectrode tip for the instrument in FIG. 1;

FIG. 5 is an enlarged top plan view of the electrode tip in FIG. 4 witha tip mounting superimposed thereon in phantom;

FIG. 6 is an enlarged sectional view of the electrode tip in FIG. 4,taken through line 6--6 of FIG. 4;

FIG. 7 is a blank of metal showing an electrode tip pattern for makingan electrode tip for the instrument in FIG. 2; and

FIG. 8 shows a plurality of electrode tips for the instrument of FIG. 2,simultaneously formed from a single metal blank, and prior to beingdetached therefrom.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Certain terminology is used herein for convenience only and is not betaken as a limitation on the present invention. The words "upper,""lower," "horizontal" and "vertical" designate directions in thedrawings to which reference is made. In the drawings, the same referencenumerals are employed for designating the same elements throughout theseveral figures.

FIG. 1 shows an electrosurgical instrument 10 in accordance with apreferred embodiment of the present invention connected to a radiofrequency (RF) output of a bipolar generator 12. Bipolar generators arewell-known in the prior art, and thus are not described in detailherein. One bipolar generator suitable for use with the instrument 10 isa CMC III bipolar generator, manufactured by Valley Forge ScientificCorp., Oaks, Pa., described in U.S. Pat. No. 5,318,563 (Malis et al.).FIG. 2 shows internal structure of an instrument 10' and FIG. 3 shows anexploded view of the main components of the instrument 10'. Theinstrument 10 shown in FIG. 1 differs in two minor ways from theinstrument 10' shown in FIGS. 2 and 3. First, the instrument 10'includes a guard 26 integrally formed with the tip of the instrument10'. The guard 26 is removed before use. In FIG. 1, the guard 26 hasalready been removed. The guard 26 is described in more detail below.Second, the instrument 10 shown in FIG. 1 includes optional irrigationmeans, whereas the instrument 10' shown in FIGS. 2 and 3 does notinclude irrigation means. For clarity, FIGS. 1-3 are described together.

Referring to FIGS. 1-3, the instruments 10 and 10' include a handle 14and an electrode tip 16. The handle 14 has a proximal end 18 and adistal end 20. The electrode tip 16 extends from the distal end 20. Theelectrode tip 16 includes a "working portion" which is generally forwardof imaginary line 1 and a "non-working portion" or base portion which isgenerally behind the imaginary line 1 (see FIGS. 1 and 3). The "workingportion" comprises that area of the electrode tip 16 which may contact apatient to cut or coagulate. The handle 14 in FIG. 1 is constructed ofintegrally joined proximal and distal portions 22 and 24 of ahigh-impact polymeric tubing material, such as extruded styrene. Thedistal portion 24 partially telescopes into the proximal portion 24 andis secured thereto with adhesive, such as epoxy or cyanoacrylate.Alternatively, the handle 14 may be constructed as a unitary piece. Thehandle 14 may optionally have circular spaced ribs (not shown) forenhanced gripping. The electrode tip 16 includes a pair of conductivemetal electrodes, an outer electrode 30 and an inner electrode 32, bothof which include a portion which extends from the distal end 20 of thehandle 14. The structure of the electrodes 30 and 32 is described inmore detail below. However, FIG. 3 (and also FIG. 4) clearly shows thatthe outer and inner electrodes 30 and 32 are not physically connected toeach other and thus some means are required for maintaining a desiredspacing therebetween. Accordingly, a T-shaped tip mounting 33 (FIG. 1)of nonconductive material maintains the outer and inner electrodes 30and 32 a fixed distance from each other and physically secures theelectrode tip 16 to the distal end of the handle 14. FIG. 3 shows thatthe tip mounting 33 is formed from two identical T-shaped pieces ofnonconductive material 33a and 33b, portions of the electrode tip 16being sandwiched therebetween. That is, portions of the electrode tip 16are encased within the tip mounting 33. The imaginary line l is colinearwith the front edge of the tip mounting 33.

Still referring to FIGS. 1-3, each of the electrodes 30 and 32 areconnected to one end of a respective insulated conductor which extendsthrough the handle 14 from the proximal end 18 to near the distal end20. Thus, the electrode 30 is connected to one end of a first insulatedconductor 34 and the electrode 32 is connected to one end of a secondinsulated conductor 36. The other ends of the first and secondconductors 34 and 36 terminate in respective connection pins 38 and 40.The insulation on opposite ends of the conductors 34 and 36 is removedto electrically connect the conductors 34 and 36 to the electrodes 30and 32 at one end, and to the pins 38 and 40 at the other end. Referringto FIG. 1, conductive wires 42 and 44 are connected at one of their endsto the connection pins 38 and 40, respectively, and are connected at theother of their ends to opposite poles of an isolated output 48 of thebipolar generator 12.

The instruments 10 and 10' each include an end cap 46 and 46',respectively, for sealing the proximal end 18 of the handle tubing andfor supporting the connection pins 38 and 40. The end cap 46 of theinstrument 10 includes additional structure to support an irrigationtube associated with the irrigation means, as described below.

Referring to FIG. 1, an optional irrigation fluid tube 50 extendsthrough the handle 12 for delivering irrigation fluid to the surgicalsite. One end of the fluid tube 50 is connected to a luer adapter (notshown) inside of the end cap 46. The other end preferably terminates atthe distal edge of the tip mounting 33, preferably extending about 1/16"beyond the tip mounting surface. The fluid tube 50 enters the tubularhandle 14 through an inlet port 52 near the proximal end 18, and exitsthe handle 14 through an outlet port 56 near the distal end 20 (which,when the instrument 10 is in use, is near the surgical site). The endcap 46 includes an extension 47 with a bore for supporting theirrigation tube 50 at the end of the handle 10. The luer is inside ofthe extension 47. Irrigation tubing 51 is connected at one end to theluer and at the other end to a source of irrigation fluid (not shown).Irrigation fluid (e.g., saline) from the fluid source is thus deliveredthrough the tubing 51, luer, and tube 50 to the surgical site.

To join the electrodes 30 and 32 into a single, unitary electrode tip 16which can be secured to the handle 14, part of non-working portions ofeach of the electrodes 30 and 32 are sandwiched between twononconductive T-shaped pieces of material 33a and 33b, best shown inFIG. 3. In a preferred embodiment of the invention all of thenon-working portions are sandwiched between the pieces of material 33aand 33b, except for terminal ends of the electrodes 30 and 32. In apreferred embodiment of the invention, the pieces of material 33a and33b are plate-like pieces of polymeric material, ultrasonically bondedto each other, to firmly hold the electrodes 30 and 32 in a fixedposition with respect to each other. Alternatively, the pieces ofmaterial 33a and 33b may be cast ceramic material held together withadhesive. Together, the pieces of material 33a and 33b form a tipmounting 33. To mount the electrode tip 16 to the handle 14, the distalend 20 of the handle 14 is heated to a pliable state. Next, the verticalportion of the tip mounting 33 is inserted into the distal end 20. Asthe distal end 20 cools, it conforms to and grips the vertical portionof the tip mounting 33. The bond may be further strengthened withadhesive, such as epoxy or cyanoacrylate.

In another embodiment of the invention, the electrode tip 16 is securedto a handle without using the tip mounting 33. In this alternativeembodiment, the handle is longitudinally divided into an upper half andlower half. The portions of the electrode tip 16 behind the imaginaryline l are seated into grooves formed in the lower half of the handle,and terminal ends of the two electrodes make positive electricalconnection to respective ends of the conductors 34 and 36. Next, theupper half of the handle is placed over the lower half and securedthereto. The electrode tip 16 is thus held in place by being partiallyseated into the grooves and sandwiched between the upper and lowerhalves of the handle. Other means for securing the electrode tip 16 tothe handle are within the scope of the invention.

FIGS. 4-6 show additional details and parameters of the electrode tip16, absent the guard 26 and tip mounting 33. In FIG. 5, the tip mounting33 is superimposed on the electrode tip 16 in phantom. As describedabove, the electrode tip 16 has a working portion and a base portion. Inaddition, each of the electrodes 30 and 32 includes a working portionand a base portion. The working portions of each electrode include theexposed loop parts of the electrodes (i.e., the portions of theelectrodes 30 and 32 which are external to the tip mounting 33 andforward of the imaginary line l). The remaining parts of the electrodes30 and 32 (the parts enclosed by the tip mounting 33) define the baseportion.

Referring to FIGS. 4 and 5, the electrode 30 includes a working portion80 and a base portion 82, and the electrode 32 includes a workingportion 84 and a base portion 86. The base portion 86 comprises ahorizontal section 94 and a lead or vertical section 92. The horizontalsection 94 bridges opposite ends of the looped working portion 84. Thevertical section 92 is connected at one end to the horizontal section94. The free end of the vertical section 92 is electrically connected toconductor 36, as shown in FIGS. 2 and 3. Together, the working portion84 and horizontal section 94 define a closed loop.

The base portion 82 of electrode 32 comprises L-shaped sections 90 and91 extending from opposite ends of the looped working portion 80. TheL-shaped section 90 includes a horizontal section 96 and verticalsection 97. The L-shaped section 91 also includes a horizontal section98 and vertical section 99. The horizontal section 96 is connected atone end to an end of the looped working portion 80, and at the other endto the vertical section 97. The free end of the vertical section 97 isused to secure the electrode 30 in proper registration with theelectrode 32 via the tip mounting 33 and to inhibit horizontal movementof the electrode 30 within the tip mounting 33. The horizontal section98 is connected at one end to the other end of the looped workingportion 80, and at the other end to the vertical section 99. The freeend of the vertical section 99 is electrically connected to conductor34, as shown in FIGS. 2 and 3. Together, the horizontal sections 96 and98 and the working portion 80 define an almost closed loop whichgenerally surrounds the closed loop of the electrode 30. Alternatively,the horizontal sections 96 and 98 and the working portion 80 may beviewed as defining a hook shape which hooks almost completely around theclosed loop of the electrode 32. Since the two electrodes 30 and 32 arecoplanar and cannot come into electrical contact with each other, theelectrode 30 cannot, by design, form a closed loop completely around theelectrode 32.

FIG. 5 shows a top plan view of the electrode tip 16 in FIG. 4. FIG. 5also shows regions of the two electrodes 30 and 32 which are encasedwithin the tip mounting 33, shown in phantom. As described above, theelectrode 30 generally surrounds the electrode 32 and is generallyspaced from and coplanar with the electrode 32. More precisely, eitherall or at least a part of the working portion 80 of the electrode 30surrounds either all or at least a part of the working portion 84 of theelectrode 32. In FIG. 5, the entire working portion 80 surrounds theentire working portion 84. As also described above, there is apredetermined distance between the electrodes 30 and 32. In onepreferred embodiment of the invention, the predetermined distance orspacing, s, is generally equal along the entire path or shape of theelectrodes 30 and 32. In another preferred embodiment of the invention,the spacing s is equal between the working portions 80 and 84, withdifferent spacings allowed between the base portions 82 and 94. However,there is always some finite spacing between the electrodes 30 and 32(i.e., s>0) so that the two electrodes 30 and 32 are never in directelectrical contact with each other. In the example where the spacing sbetween the working portions 80 and 84 of the electrodes 30 and 32 isequal, it can be said that the electrode 30 is equidistant from theelectrode 32. In the figures, the spacing s is equal along the entirepath of the electrodes 30 and 32. The scope of the invention alsoincludes embodiments wherein the spacing s between the working portions80 and 84 of the electrodes 30 and 32 is unequal. For example, thespacing s near the apex of the arc defined by the working portions maybe different than the spacing s near the edge regions of the workingportions. It may be desirable to have greater or less spacing s near theapex of the arc defined by the working portions than near the edgeregions of the working portions.

The electrode tip 16 and electrodes 30 and 32 have defined dimensionsand parameters. The tip mounting 33 is shown in FIG. 5 because certaindimensions of the electrode tip 16 are defined in relationship to thetip mounting 33, or to other structure that performs the same functionas the tip mounting 33. The maximum horizontal distance of the electrodetip 16 is defined as the width, w_(t), of the working portion 84 of theelectrode 32. The width, w_(t), is the distance between opposite exposedends of the working portion 84 of the electrode 32. The height of theelectrode tip 16 is defined as the height, h_(t), from the oppositeexposed ends of the working portion 84 of the electrode 32 to apex 100of the arc in the working portion 84 of the electrode 32. (The height ofthe electrode tip 16 is thus defined by dimensions of the innerelectrode 32, not the outer electrode 30.) The electrode tip 16 also hasa loop ratio, defined as the ratio of the absolute distance of theworking portion 84 vs. the absolute distance of the working portion 80.The leads or vertical sections 98 and 92 have predefined lengths l_(e1)and l_(e2), respectively.

Referring to FIGS. 4, 5 and 6 (especially, FIG. 6), the working portion80 of the electrode 30 has a flat upper surface 102, a flat lowersurface 104, and squared off sharp corners or edges 106. Likewise, theworking portion 84 of the electrode 32 has a flat upper surface 108, aflat lower surface 110, and squared off sharp corners or edges 112. Inthe embodiment of the invention shown in the figures, the base portions82 and 86 also have flat upper and lower surfaces, and sharp edges, dueto the method of fabricating the electrodes 30 and 32. The base portions82 and 86 need not have either of these features. The working portions80 and 84 are circumferentially unattached to any surrounding structure,and the material of the electrodes 30 and 32 is continuous (i.e.,unbroken) through their respective working portions 84 and 80. As aresult of these features, at least the working portions 80 and 84 of theelectrodes 30 and 32 are generally rectangular in cross-section and thusare defined by a thickness and a width. The area of the rectangularcross-section is generally uniform throughout the working portion. Sincethe electrodes 30 and 32 are coplanar, they have equal thicknesses,t_(e). The widths of the electrode working portions 80 and 84 may beequal or different. In the figures, the electrodes 30 and 32 havedifferent working portion widths w_(e1) and w_(e2), respectively. Widthsof the horizontal sections 94, 96 and 98, and the leads or verticalsections 92 and 99 are significantly larger than the widths of theworking portion 80 and 84. A preferred embodiment of the electrode tip16, has the following approximate range of dimensions and parameters:

    ______________________________________    spacing, (s)     0.035" (0.89 mm.)    width of electrode tip (w.sub.t)                     0.20" to 0.98" (5 mm. to 25 mm.)    height of electrode tip (h.sub.t)                     0.20" to 0.59" (5 mm. to 15 mm.)    length of vertical section 99 (l.sub.e1)                     0.50" (12.7 mm.)    length of vertical section 92 (l.sub.e2)                     0.54" (13.6 mm.)    loop ratio       1:11/2    thickness of electrodes (t.sub.e)                     0.005" to 0.015" (0.13 mm.                     to 0.38 mm.)    width of electrode 30 (w.sub.e1)                     0.009" (0.23 mm.)    width of electrode 32 (w.sub.e2)                     0.006" (0.15 mm.)    width of horizontal sections 90,                     0.059" (1.5 mm.)    94 and 96    width of vertical sections 92                     0.039" (1.0 mm.)    and 98    electrode 30 and 32 material                     stainless steel, tungsten, titanium,                     tungsten deposited on stainless steel,                     INCONEL, (a nickel and chromium                     alloy) or other metallic alloys    ______________________________________

Some examples of suitable width and height combinations for electrodetips include 25×15, 20×10, 20×7, 15×10, 15×7, 10×10, 10×7, 5×10, 5×5 and3×5, wherein the first dimension is the width (w_(t)) in mm. and thesecond dimension is the height (h_(t)) in mm. FIGS. 4-6 show a 20×10 mm.tip having a thickness of about 0.015" (0.38 mm.).

One preferred method of fabricating the electrode tip 16 is by photochemical machining. Referring to FIG. 7, the process begins with a metalblank 114, such as stainless steel, having a thickness t_(e) and flatupper and lower surfaces 116 and 118. The metal blank 114 is precoatedwith photoresist materials of common usage. A pattern 120 and its mirrorimage 120' are created by standard drafting techniques and arephotographically transferred (in negative form) to transparent film. Thepatterns 120 and 120' may also be reduced in size to reduce drawing linewidths and to achieve proper final product size. Next, properly sizedpatterns 120 and 120' are placed in contact with respective upper andlower surfaces 116 and 118 of the metal blank 114, in properregistration and alignment with each other. The pattern 120 on the uppersurface 116 is in solid lines and the pattern 120' on the lower surface118 is in phantom. Using a vacuum table (not shown), the upper and lowerpatterns 120 and 120' are held closely to the metal blank 114 while anarc lamp 121 exposes the photoresist in the area where the negativepatterns are transparent. Next, the metal blank 114 is removed anddeveloped in the same manner as a negative photograph is developed. Thedeveloping process chemically hardens the photoresist in areas exposedto the arc lamp 121. The unexposed and undeveloped photoresist is washedaway. Next, the metal blank 114 is exposed to chemicals commonly used inthe art to dissolve metal not covered with photoresist. Chromic acid,ferric chloride, or other etch chemicals may be used. After etching, theremaining metal is a faithful reproduction, in metal, of the pattern120, including at least the electrodes, a carrier and a protective guardstructure, and support and tab structures, all for use duringpost-manufacturing handling. For simplicity, FIG. 7 does not show thepatterns which form the additional non-electrode structures. Thesepatterns are shown in FIG. 8.

The resultant piece of metal has the shape of the created pattern, andis thus identical to FIGS. 4 and 5. That is, the resultant piece ofmetal is the shape of the electrodes 30 and 32. Since the metal blank114 has flat upper and lower surfaces 116 and 118, the resultantelectrodes 30 and 32 are coplanar and have sharp edges in cross-section.The resultant electrode tip 16 (i.e., electrodes 30 and 32) is mountedor inserted into the distal end 20 of the handle 14 and engagesconductors 34 and 36 to establish positive electrical contacttherebetween, as shown in FIG. 3, to create the electrosurgicalinstrument 10.

The electrode tip 16 is very delicate and should be protected fromphysical contact until it is ready to be used. Also, the relativeregistration of the electrodes 30 and 32 must be maintained because thetwo electrodes are not physically connected to each other at any point.To protect the electrode tip 16 and to maintain proper relativeregistration between the electrodes 30 and 32, it is preferred tofabricate the electrode tip 16 with a guard, supports, a carrier andtabs therebetween, and to install the tip mounting 33 after fabricationbut before removal of the supports 124 or guard 26.

When electrode tips 16 are made by the process described above, pluralelectrode tips 16 of the same or different width and height combinationsmay be simultaneously fabricated from a single metal blank. Thus,significant manufacturing efficiencies can be achieved.

FIG. 8 shows eight electrode tips 16₁ through 16₈ fabricated from asingle metal blank 115 and illustrates all of these above-mentionedfeatures. In FIG. 8, each electrode tip 16₃ through 16₈ has a differentwidth and height combination. Prior to being etched, a pattern including(1) a peripheral carrier pattern, (2) an electrode pattern for each ofthe electrode tips 16₁ through 16₈, and (3) associated support patterns,tab patterns and a guard pattern for each electrode pattern, is placedagainst both surfaces of the metal blank 115, as described above. Thepatterns form the electrode tips 16₁ through 16₈, peripheral carrier122, support plates or supports 124, guards 26 and tabs 128 in theresultant metal blank of FIG. 8. To install a particular electrode tip16 into a handle 14, an electrode tip 16 and corresponding supports 124and guard 26 is removed from the carrier 122. Next, non-working portionsof the electrode tip 16 are sandwiched between the two T-shaped piecesof material 33a and 33b. The pieces of material 33a and 33b are securedto each other and to the electrode tip 16, such as by ultrasonic bondingto form the tip mounting 33. (Alternatively, the non-working portions ofthe electrode tip 16 may be sandwiched between the two T-shaped piecesof material 33a and 33b while the electrode tip 16 is still in thecarrier 122.) The tip mounting 33 encases all but the working portion ofthe electrode tip 16 and the terminal ends of each individual electrode.As a result, the tip mounting 33 maintains relative registration of theworking portions of the two electrodes. Next, the supports 124 andrelated tabs 128 are removed. One end of the first and second conductors34 and 36 are connected to respective terminal ends of the electrodes 30and 32, such as by soldering or welding. The conductors 34 and 36 arefitted through the distal portion of the handle 14. The electrode tip16, with the guard 26 still intact, is then installed into the distalend of the distal portion 24 of the handle 14, in accordance with theprocedure described above with respect to FIGS. 1-3. FIG. 2 shows onesuch guard 26 attached to the electrode tip 16 of a fully assembledinstrument 10. Immediately before use, the guard 26 is snapped off.

While the photo chemical etching process is used to fabricate the entireelectrode tip 16 in one step, the method may be used to separatelyfabricate each electrode 30 and 32. The photo chemical etching processmay be replaced by other processes which can achieve a similar resultfrom a metal blank. Other potential techniques include laser cutting,mechanical microcutting techniques or other techniques which can formelectrodes having sharp edges and working portion dimensions definedabove.

When fabricating electrode tips by the process shown in FIG. 8, the tipsmay be colored to quickly identify different sized electrodes. Forexample, titanium electrodes tips may be colored by anodizing.

Electrode tip sizes are selected according to the desired application(e.g., neurosurgery, obstetrics/gynecology surgery) and structure of thesurgical site. For example, a long, narrow tip should be used when thesurgical site is a narrow cavity.

The guard 26 may be replaced by other guard structure which need not beintegrally formed with the electrode tip 16. It is also within the scopeof the invention to make the electrodes 30 and 32 without the carrier122, supports 124, guards 26 and tabs 128. Instead, the electrodes 30and 32 may be carefully handled after fabrication and secured in a fixedrelationship to each other, and to a handle, by other suitable means.

The instrument 10 is meant to be disposable, although it is within thescope of the invention to reuse any parts of the instrument 10 which arenot degraded during use and which can be adequately sterilized.

The loop shaped working portion of the electrodes 30 and 32 may begenerally circular, semicircular, parabolic or rectangular in shape.

The electrodes 30 and 32 in the present instrument have sharp edges 106and 112 in cross-section, in contrast to prior art wire electrodes whichdo not have sharp edges in cross-section. The sharp edges concentratethe contact area and improve the concentration of energy at the surgicalsite in comparison to the wire electrodes. In use, when power is appliedto the electrode tip 16, energy distributes evenly along the length ofthe electrode working portions 80 and 82. The energy also emits radiallyfrom the working portions 80 and 82. However, the emitted RF energyconcentrates and focuses at the edges 106 and 112 instead of radiallyemitting equally in all directions as in prior art wire electrodes. Forat least this reason, the electrodes 30 and 32 formed by the processdescribed above evidence lower resistance to cutting than the prior artwire electrodes. Thus, less power may be applied to the electrodes 30and 32 to achieve the same cutting/coagulating effect as the prior artwire electrodes. By using less power at the surgical site, the devicecan be used in delicate surgical procedures, such as neurosurgery, withless risk of disturbing neighboring tissue or organs.

Furthermore, the electrodes 30 and 32 may be fabricated to besignificantly finer than what is currently achievable using wireelectrodes. For example, the smallest disclosed wire diameter in U.S.Pat. Nos. 5,282,799 (Rydell) and 5,192,280 (Parins) is 0.010 inches(0.254 mm.), providing a cross-sectional area of 0.05 mm² (0.7854×d²=0.7854×(0.254)² =0.05). In contrast, electrode 30 may have a width assmall as about 0.006" (0.15 mm.) and a thickness as small as 0.0051"(0.13 mm.), thereby providing a cross-sectional area as small as about0.02 mm² (w×t=0.15×0.13=0.02), measurably finer than the cross-sectionalarea of the wire electrode.

Referring to FIG. 6, the electrodes 30 and 32 are ideally rectangular incross-section. However, it is difficult to produce perfectly rectangularshaped electrodes using the chemical etching process described herein.The fabricated electrodes may have regions of slight concavity along theside edges, giving a slightly hourglass shape to the electrodes incross-section. Such electrodes still possess the advantages describedabove because they still have relatively sharp edges. One way tominimize the concavity when etching from one side only is to etch abouthalfway through the blank, and then turn the blank over and etch throughthe other side.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

We claim:
 1. A method of fabricating at least one electrode from a metalblank, the method comprising the steps of:(a) creating at least onepattern, the pattern including at least an electrode pattern; (b)placing a negative of the pattern against opposite facing surfaces of ametal blank coated with a photoresist material, the negative of thepattern on the opposite facing surfaces being in registration with eachother; (c) exposing and developing the metal blank, and removingphotoresist from unexposed, undeveloped areas of the metal blank; and(d) exposing the metal blank to a metal dissolving chemical that etchesaway the unexposed, undeveloped areas of the metal blank, the resultantpiece of metal being suitable for use as at least one electrode, theresultant piece of metal having a shape of the at least one createdelectrode pattern and having a working portion with sharp edges incross-section.
 2. A method according to claim 1 wherein the pattern instep (a) includes a guard pattern, the at least one electrode patternbeing joined to the guard pattern at at least two points, the resultantpiece of metal being suitable for use as at least one electrode and aguard for the at least one electrode, the resultant piece of metalhaving a shape of the at least one created electrode pattern and theguard pattern.
 3. A method according to claim 2 wherein the pattern instep (a) includes a tab pattern, the tab pattern joining the guardpattern and the at least one electrode pattern, the electrode and guardon the resultant piece of metal being joined at tabs formed from the tabpattern.
 4. A method according to claim 1 wherein the working portion ofthe resultant piece of metal is generally rectangular in cross-section.5. A method according to claim 1 wherein the metal blank is formed fromthe group of materials consisting of stainless steel, tungsten, a nickeland chromium alloy and titanium.
 6. A method according to claim 1wherein the electrode pattern is generally loop shaped.
 7. A methodaccording to claim 1 wherein the pattern in step (a) includes aplurality of electrode patterns, the resultant piece of metal beingsuitable for use as multiple, individual electrodes.
 8. A methodaccording to claim 1 wherein the pattern in step (a) includes a carrierpattern, the at least one electrode pattern being joined to the carrierpattern at at least one point, the resultant piece of metal beingsuitable for use as at least one electrode and a carrier for the atleast one electrode, the resultant piece of metal having a shape of theat least one created electrode pattern and the carrier pattern.
 9. Amethod of fabricating at least one electrode tip from a single metalblank, the method comprising the steps of:(a) creating at least onepattern, the pattern including at least an electrode tip pattern; (b)placing a negative of the pattern against opposite facing surfaces of asingle metal blank coated with a photoresist material, the negative ofthe pattern on the opposite facing surfaces being in registration witheach other; (c) exposing and developing the metal blank, and removingphotoresist from unexposed, undeveloped areas of the metal blank; and(d) exposing the metal blank to a metal dissolving chemical that etchesaway the unexposed, undeveloped areas of the metal blank, the resultantpiece of metal being suitable for use as at least one electrode tip, theresultant piece of metal having a shape of the at least one createdelectrode tip pattern and having a working portion with sharp edges incross-section.
 10. A method according to claim 9 wherein the workingportion of the created electrode tip pattern is a first loop shape and asecond loop shape spaced from and generally surrounding at least aportion of the first loop shape.
 11. A method according to claim 9wherein the working portion of the created electrode tip pattern is aloop shape and a hook shape spaced from and generally surrounding atleast a portion of the loop shape.
 12. A method according to claim 9wherein step (a) includes creating multiple electrode tip patterns, theresultant piece of metal being suitable for use as multiple, individualelectrode tips.
 13. A method of making an electrode instrumentcomprising the steps of:(a) fabricating an electrode tip from a singlemetal blank by(i) creating at least one pattern, the pattern includingat least an electrode tip pattern, the electrode tip pattern being aloop shape and a hook shape spaced from and generally surrounding atleast a portion of the loop shape, (ii) placing a negative of thepattern against opposite facing surfaces of the single metal blankcoated with a photoresist material, the negative of the pattern on theopposite facing surfaces being in registration with each other; (iii)exposing and developing the metal blank, and removing photoresist fromunexposed, undeveloped areas of the metal blank; and (iv) exposing themetal blank to a metal dissolving chemical that etches away theunexposed, undeveloped areas of the metal blank, the resultant piece ofmetal being suitable for use as at least one electrode tip having afirst electrode in the form of a loop and a second electrode in the formof a hook spaced from and generally surrounding at least a portion ofthe loop, the resultant first and second electrodes having workingportions with sharp edges in cross-section; (b) mounting the electrodetip to a distal end of a handle; and (c) connecting the first and secondelectrodes to conductors which extend through the handle and are adaptedto connect to respective opposite poles of a bipolar generator.
 14. Amethod of making an electrode instrument according to claim 13 whereinthe first and second electrodes each have a non-working portion, andstep (b) is performed by:(i) sandwiching at least a part of thenon-working portion of the first and second electrodes between first andsecond generally T-shaped pieces of material and attaching the pieces ofmaterial to each other together, the pieces of material together forminga tip mounting for maintaining the first and second electrodes in thespaced relationship, and (ii) attaching a vertical portion of the tipmounting to the distal end of the handle.
 15. A method of fabricating anelectrode tip from a metal blank, the method comprising the steps of:(a)defining a pattern, the pattern including an electrode tip; and (b)machining the metal blank as defined by the pattern to form at least theelectrode tip, the resultant electrode tip having a working portion withsharp edges in cross-section.
 16. A method according to claim 15 whereinthe pattern in step (a) includes a guard pattern, the at least oneelectrode tip pattern being joined to the guard pattern at at least twopoints, the machined metal blank being suitable for use as at least oneelectrode tip and a guard for the at least one electrode tip.
 17. Amethod according to claim 16 wherein the pattern in step (a) includes atab pattern, the tab pattern joining the guard pattern and the at leastone electrode tip pattern, the electrode and guard on the machined metalblank being joined at tabs formed from the tab pattern.
 18. A methodaccording to claim 15 wherein the machining is performed by a photochemical machining process.
 19. A method according to claim 15 whereinthe metal blank is formed from the group of materials consisting ofstainless steel, tungsten, a nickel and chromium alloy and titanium. 20.A method according to claim 15 wherein the defined pattern is generallyloop shaped.
 21. A method according to claim 16 wherein the pattern instep (a) includes a plurality of electrode tip patterns, the machinedmetal blank being suitable for use as multiple, individual electrodetips.
 22. A method according to claim 16 wherein the pattern in step (a)includes a carrier pattern, the at least one electrode tip pattern beingjoined to the carrier pattern at at least one point, the machined metalblank being suitable for use as at least one electrode tip and a carrierfor the at least one electrode tip.
 23. A method according to claim 15wherein steps (a) and (b) are performed on a metal blank having across-sectional thickness of about 0.13 mm to about 0.38 mm, theresultant electrode tip working portion thereby having a cross-sectionalthickness of about 0.13 mm to about 0.38 mm.
 24. A method according toclaim 15 wherein in step (a), the electrode tip pattern has across-sectional width of about 0.15 mm or about 0.23 mm, the resultantelectrode tip working portion thereby having a cross-sectional width ofabout 0.15 mm or about 0.23 mm.
 25. A method according to claim 15wherein in step (a), the electrode tip pattern is a continuous pattern.